A prior art example will be described with reference to FIG. 17. FIG. 17 is a block diagram illustrating the configuration of a conventional signal transmission system.
In FIG. 17, reference numeral 1701 denotes a video signal output unit (transmitting end) such as a STB (Set-top box), which outputs a video signal. Numeral 1702 denotes an MPEG decoder, which receives digital broadcasting and outputs baseband Y color-difference signals. Numeral 1703 denotes a signal conversion circuit, which converts the Y color-difference signals into RGB signals. Numeral 1704 denotes a transmission path encoding circuit, which encodes the signals converted by the signal conversion circuit 1703 into signals in formats suited to the transmission path. Numeral 1705 denotes a display unit (receiving end) such as a TV monitor. Numeral 1706 denotes a transmission path decoding circuit, which decodes the signals encoded by the transmission path encoding circuit 1704. Numeral 1707 denotes a signal conversion circuit, which converts the RGB signals outputted from the transmission path decoding circuit 1706 into YPBPR signals. Numeral 1708 denotes a Y processing circuit, which processes luminance signals Y out of the output from the signal conversion circuit 1707. Numeral 1709 denotes a chrominance processing circuit, which processes chrominance signals out of the output from the signal conversion circuit 1707. Numeral 1710 denotes a signal conversion circuit, which receives the outputs from the Y processing circuit 1708 and the chrominance processing circuit 1709 and converts the Y color-difference signals into the RGB signals. Numeral 1711 denotes a display device, which receives the output from the signal conversion circuit 1710 and outputs it to a LCD or CRT.
An operation of the so-configured signal transmission system will be described.
The MPEG decoder 1702 receives digital broadcasting and outputs baseband video signals. As the data format of the MPEG is based on Y color-difference signals, the output here is YPBPR, or YUV, or YCbCr. Further, this signal must be converted into RGB signals to encode it adaptively to a transmission path, and thus the Y color-difference signals are converted into RGB signals by the signal conversion circuit 1703. The converted RGB signals are encoded into signal forms suited to the transmission path by the transmission path encoding circuit 1704.
On the other hand, on the TV monitor 1705 side, the transmission path decoding circuit 1706 receives the signals encoded by the transmission path encoding circuit 1704 and generates the original RGB signals. The RGB signals are converted into the YPBPR of the Y color-difference signals by the signal conversion circuit 1707. Here, to perform independent processing on the TV monitor 1705 side, the Y signals are processed by the Y processing circuit 1708, and the chrominance signals PBPR are enhanced by the chrominance processing circuit 1709, respectively, and these signals are outputted. The enhanced and outputted Y color-difference signals are converted into the RGB signals by the signal conversion circuit 1710 so as to be outputted to the final display device 1711. The display device 1711 outputs the RGB signals which have been outputted from the signal conversion circuit 1710, thereby to perform display.
However, in the above-described conventional signal transmission system, since the transmission path encoding is performed on the RGB signals, the output from the MPEG decoder is once converted into the RGB signals, encoded, and transmitted through the transmission path and, thereafter, the RGB signals must be converted into the YPBPR to perform signal processing again on the monitor side and, further, the Y color-difference signals must be converted into the RGB signals once again to output the RGB signals to the final display device, resulting in a drawback of requiring a lot of hardware.
The present invention is made to solve the above-mentioned problems and has for its object to provide a signal transmission system in which hardware configurations of the video signal transmitting end and receiving end can be simplified